Pain from the Interstate 215 Spring Sting construction project in Grand Terrace is nearing an end this weekend, on schedule, with a final freeway closure and fewer than expected headaches.

Caltrans officials said they’re wrapping up installation of two towering steel train bridges across the freeway with final closures from 11:30 p.m. today to 6 a.m. Thursday for northbound lanes, followed by both directions being shut down from 11:30 p.m. Friday to 11:30 a.m. Saturday.

Construction is optional on Sunday, but will likely not be needed, officials said.

Commuters are encouraged to take alternate routes such as the 10, 15 and 60 freeways to avoid the estimated 1/2-mile stretch of Interstate 215 between Iowa Avenue and Barton Road, between Riverside and San Bernardino in Grand Terrace. And they have been, traffic officials said.

“We haven’t received any complaints at all. Not one. Everyone took heed and diverted their trips” said Caltrans spokeswoman Terri Kasinga.

Another possible contributing factor to less commuter frustration than normal was the innovative process used to replace the bridges, said San Bernardino County Supervisor James Ramos, who sits on the SanBAG Commuter Rail and Transit Committee.

These bridges were constructed off-site then moved into place. The typical conventional process involves building the bridges on-site over the freeway. Ramos said the off-site process saved time and averted long-term traffic challenges would could have added to an already difficult drive through the busy corridor.

Innovation, however, can also mean a potential for complication.

“These kinds of things are new and innovative, and things we don’t see every day, and things can go wrong,” said Kasinga.

But this project remained on schedule.

The same construction process is planned for a third bridge replacement in August or September. All three are expected to be operational by early 2015.

The train trestle project is part of a major $176 million project to install carpool lanes on the 215 from Riverside to San Bernardino. Money for the construction comes from Measure I and federal and state funding.